typically the shoulder area carries the most rings from the chamber reamer, mostly due to the angle of the cutting surface to the material, any imperfection in the tools surface is transfered to the shoulder. If a chip welds itself to the reamers cutting surface the rings will be more prominent.

Bore scoping during the chamber job is the time to find and correct these small issues. a light polish of the shoulder after reaming will also lessen the prominence of these rings.

Yours look quite distinct so my guess is he spun a chip or had some chip weld on the reamers cutting surface, I'm sure your smith would correct it if you brought it to his attention. One other cause is a barrel with a hard spot that cut difficult and may tear a bit. I had one barrel in 250 that did that so not real common.

Fliers I believe has to do with uneven neck tension created by something in the chamber neck area here take a look every brass fired through has exact signature at the tip of the neck, its not all away around just about 1/4 of the neck , and carbon escape also in exact spot...